DWTS: Peta & James Knew from Day One They Could Make It to the Finals

It's crunch time on Dancing with the Stars, and Peta Murgatroyd and James Maslow are one of four couples heading into next week's fight for the mirror ball trophy after surviving elimination during Monday night's semifinals.

"I knew we could do it," Murgatroyd, 27, told PEOPLE backstage after the show, reflecting on her and Maslow's first rehearsals at the beginning of the season.

Added Maslow, 23: "We couldn't have predicted the path of who would have been voted off each week. I think because it's been so strange and seemingly random, we were confident in what we could do, but you can never be too confident in staying. So we've got to keep that humility, and we've got to do better than we've done each week and that's all we can do."

After completing two routines on Monday, the pair was only four points shy of a perfect 80-point total. But going into the show, Maslow was coming off of a bout with food poisoning.

"I was in bed yesterday as soon as I left rehearsal," he said. "Luckily, I think it's just a 24-hour thing, so I'm starting to feel better. I'm going to try and get some actual real food in me after this. That would slow anyone's day down."

Now, as they look ahead to next week, they need to ace their freestyle – something Murgatroyd did when she won the mirror ball with Donald Driver during season 14.

"Hell yeah, we're going to be able to top that," the pro dancer said. "Donald texted us the other day, saying congratulations, and he was like, 'I might see another mirror ball coming your way soon.' He's really awesome."

Moving into this week of rehearsals, Murgatroyd calls it "do or die" time.

"It's such an important week," she said. "We need to bond more than ever this week and make sure we collaborate with all the ideas and just make sure we're on the same page and just kill this freestyle."

The pair will face off against Candace Cameron Bure and Mark Ballas; Amy Purdy and Derek Hough; and Meryl Davis and Maksim Chmerkovskiy.